Methods and Devices for Enhancing Chemical Mechanical Polishing Processes

ABSTRACT

The present invention discloses methods and systems for increasing polishing performance of a CMP process. In one aspect, for example, a method of increasing polishing performance of a CMP process includes vibrating a contact interface between a CMP pad and a wafer during a CMP process, such that oscillations between the CMP pad and the wafer occurs in a direction substantially parallel to a working surface of the CMP pad. In one specific aspect, vibrating the contact interface includes vibrating the contact interface in a direction substantially parallel to the contact interface. The vibrating can include vibrating the CMP pad, vibrating the wafer, or vibrating the CMP pad and the wafer. Such vibrations can allow the contact pressure at the contact interface to be decreased as compared to a contact interface that is not vibrated to minimize damage to the CMP pad or the wafer.

PRIORITY DATA

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/606,365, filed on Nov. 27, 2006, which is incorporatedherein by reference. This application is also a continuation-in-part ofU.S. patent application Ser. No. 12/346,264, filed on Dec. 30, 2008,which is a continuation-in-part of U.S. patent application Ser. No.11/349,034, filed on Feb. 6, 2006, both of which are incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates generally to methods and devices forchemical mechanical processing. Accordingly, the present inventioninvolves the fields of chemistry, metallurgy, mechanics and materialsscience.

BACKGROUND OF THE INVENTION

Chemical mechanical process (CMP), also know as chemical mechanicalplanarization or chemical mechanical polishing, has become a widely usedtechnique for polishing certain work pieces. Particularly, the computermanufacturing industry has begun to rely heavily on CMP processes forpolishing wafers of ceramics, silicon, glass, quartz, metals, andmixtures thereof for use in semiconductor fabrication. Such polishingprocesses generally entail applying the wafer against a rotating padmade from a durable organic substance such as polyurethane.Additionally, a slurry of a chemical solution capable of breaking downthe wafer substance, and a sufficient amount of abrasive particles isadded to the pad to further aid in the polishing of the wafer surface.The slurry is continually added to the rotating CMP pad, and the dualchemical and mechanical forces exerted on the wafer cause it to polishor planarize in a desired manner.

In a typical polishing process, the working surface of the pad holds theslurry containing the abrasive particles, usually by a mechanism such asfibers, asperities or small grooves, which provide a friction forcesufficient to prevent the particles from being thrown off of the pad dueto the centrifugal force exerted by the pad's spinning motion.Therefore, it is important to assure that there are an abundance ofopenings and grooves available on the pad surface to receive new slurry.

A problem with maintaining the working surface of the pad is caused byan accumulation of polishing debris coming from the work piece, abrasiveslurry, and dressing disk. This accumulation causes a “glazing” effect,or hardening of the working surface of the pad, and wears or mats thefibers down. Thus, the pad is less able to hold the abrasive particlesof the slurry, and the pad's overall polishing performance issignificantly decreased. Further, with many pads, the grooves used tohold the slurry become clogged, and the pad's polishing surface becomesdepressed and matted. Therefore, attempts have been made to revive thesurface of the pad by “grooming” or “cutting” grooves and formingasperities on the surface with various devices. This process has come tobe known as “grooming”, “dressing” or “conditioning” the CMP pad. Manytypes of devices and processes have been used for this purpose. One suchdevice is a disk with a plurality of superabrasive particles, such asdiamond particles, attached to a surface or substrate thereof.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides methods and systems forincreasing polishing performance of a CMP process. In one aspect, forexample, a method of increasing polishing performance of a CMP processincludes vibrating a contact interface between a CMP pad and a waferduring a CMP process, such that oscillations between the CMP pad and thewafer occurs in a direction substantially parallel to a working surfaceof the CMP pad. In one specific aspect, vibrating the contact interfaceincludes vibrating the contact interface in a direction substantiallyparallel to the contact interface. The vibrating can include vibratingthe CMP pad, vibrating the wafer, or vibrating the CMP pad and thewafer. Such vibrations can allow the contact pressure at the contactinterface to be decreased as compared to a contact interface that is notvibrated to minimize damage to the CMP pad or the wafer.

Various vibration parameters are contemplated, and any vibrationparameter that increases polishing performance should be considered tobe within the present scope. In one aspect, non-limiting examples ofvibrations at the contact interface include lateral motions, circularmotions, elliptical motions, random motions, and combinations thereofAdditionally, the vibrating of the contact surface can be varied in avariety of ways, for example, by varying the vibration frequency,varying the vibration amplitude, or varying the vibration frequency andthe vibration amplitude. Additionally, the vibrations at the contactsurface can be at ultrasonic frequencies and non-ultrasonic frequencies.For example, in one aspect the contact surface can be vibrated at anultrasonic frequency greater than about 15 kHz. Furthermore, thevibration can be a continuous vibration, an intermittent vibration,and/or two or more superimposed vibrations.

In another aspect, the present invention provides a CMP system,including a CMP pad, a wafer positioned to contact the CMP pad during apolishing procedure at a contact interface, and a vibration systemfunctionally coupled to at least one of the CMP pad and the wafer, wherethe vibration system is operable to cause vibrations at the contactinterface in a direction substantially parallel to the contactinterface.

There has thus been outlined, rather broadly, the more importantfeatures of the invention so that the detailed description thereof thatfollows may be better understood, and so that the present contributionto the art may be better appreciated. Other features of the presentinvention will become clearer from the following detailed description ofthe invention, or may be learned by the practice of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Before the present system and associated methods are disclosed anddescribed, it is to be understood that this invention is not limited tothe particular process steps and materials disclosed herein, but isextended to equivalents thereof as would be recognized by thoseordinarily skilled in the relevant arts. It should also be understoodthat terminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” and, “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to a “transducer” includes reference to one or more of suchtransducers.

Definitions

In describing and claiming the present invention, the followingterminology will be used in accordance with the definitions set forthbelow.

As used herein, “abrasive particle,” or “grit,” or similar phrases meanany super hard crystalline, or polycrystalline substance, or mixture ofsubstances and include but are not limited to diamond, polycrystallinediamond (PCD), cubic boron nitride (cBN), and polycrystalline cubicboron nitride (PCBN). Further, the terms “abrasive particle,” “grit,”“diamond,” “polycrystalline diamond (PCD),” “cubic boron nitride (cBN)”and “polycrystalline cubic boron nitride, (PCBN),” may be usedinterchangeably.

As used herein, “superhard” and “superabrasive” may be usedinterchangeably, and refer to a crystalline, or polycrystallinematerial, or mixture of such materials having a Vicker's hardness ofabout 4000 Kg/mm² or greater. Such materials may include withoutlimitation, diamond, and cubic boron nitride (cBN), as well as othermaterials known to those skilled in the art. While superabrasivematerials are very inert and thus difficult to form chemical bonds with,it is known that certain reactive elements, such as chromium andtitanium are capable of chemically reacting with superabrasive materialsat certain temperatures.

As used herein, “vibrate” means to oscillate an object in asubstantially horizontal direction, back and forth or from side to side,in a rapid movement. Vibrations may be continuous, intermittent,continuously variable, in accordance with a vibrational program, etc.Accordingly, a CMP pad, CMP pad dresser, wafer, or superabrasiveparticles of a CMP pad dresser can be vibrated at a desired frequency toobtain an optimal polishing performance.

As used herein, “contact interface” refers to a plane of contact betweentwo devices, such as between a CMP pad and a wafer.

As used herein, “ultrasonic” means any energy wave that vibrates withfrequencies higher than those audible to the human ear. For example suchfrequencies are higher frequencies than about 15,000 Hz, or in otherwords more than about 15,000 cycles per second.

As used herein, “substrate” means a portion of a CMP dresser whichsupports abrasive particles, and to which abrasive particles may beaffixed. Substrates useful in the present invention may be any shape,thickness, or material, which is capable of supporting abrasiveparticles in a manner that is sufficient to provide a tool useful forits intended purpose. Substrates may be of a solid material, a powderedmaterial that becomes solid when processed, or a flexible material.Examples of typical substrate materials include without limitation,metals, metal alloys, ceramics, and mixtures thereof. Further, thesubstrate may include brazing alloy material.

As used herein, “quality” means a degree or grade of excellence. Eachcharacteristic or property of a superabrasive particle such as internalcrystalline perfection, shape, etc. may be ranked in order to determinethe quality of the particle. A number of established quality scalesexist in the area of diamonds and other superabrasives, such as theGemological Institute of America (GIA) Diamond Grading Report or the GIAScale, which will be well recognized by those of ordinary skill in theart.

As used herein, “amorphous braze” refers to a homogenous brazecomposition having a non-crystalline structure. Such alloys containsubstantially no eutectic phases that melt incongruently when heated.Although precise alloy composition is difficult to ensure, the amorphousbrazing alloy as used herein should exhibit a substantially congruentmelting behavior over a narrow temperature range.

As used herein, “alloy” refers to a solid or liquid mixture of a metalwith a second material, said second material may be a non-metal, such ascarbon, a metal, or an alloy which enhances or improves the propertiesof the metal.

As used herein, “metal brazing alloy,” “brazing alloy,” “braze alloy,”“braze material,” and “braze,” may be used interchangeably, and refer toa metal alloy which is capable of chemically bonding to superabrasiveparticles, and to a matrix support material, or substrate, so as tosubstantially bind the two together. The particular braze alloycomponents and compositions disclosed herein are not limited to theparticular embodiment disclosed in conjunction therewith, but may beused in any of the embodiments of the present invention disclosedherein.

As used herein, the process of “brazing” is intended to refer to thecreation of chemical bonds between the carbon atoms of the superabrasiveparticles and the braze material. Further, “chemical bond” means acovalent bond, such as a carbide or boride bond, rather than mechanicalor weaker inter-atom attractive forces. Thus, when “brazing” is used inconnection with superabrasive particles a true chemical bond is beingformed. However, when “brazing” is used in connection with metal tometal bonding the term is used in the more traditional sense of ametallurgical bond. Therefore, brazing of a superabrasive segment to atool body does not require the presence of a carbide former.

As used herein, “chemical bond” and “chemical bonding” may be usedinterchangeably, and refer to a molecular bond that exerts an attractiveforce between atoms that is sufficiently strong to create a binary solidcompound at an interface between the atoms.

As used herein, in conjunction with the brazing process, “directly” isintended to identify the formation of a chemical bond between thesuperabrasive particles and the identified material using a singlebrazing metal or alloy as the bonding medium.

As used herein, “ceramic” refers to a hard, often crystalline,substantially heat and corrosion resistant material which may be made byfiring a non-metallic material, sometimes with a metallic material. Anumber of oxide, nitride, and carbide materials considered to be ceramicare well known in the art, including without limitation, aluminumoxides, silicon oxides, boron nitrides, silicon nitrides, siliconcarbides, tungsten carbides, etc.

As used herein, “metallic” means any type of metal, metal alloy, ormixture thereof, and specifically includes but is not limited to steel,iron, and stainless steel.

As used herein, “grid” means a pattern of lines forming multiplesquares.

As used herein, with respect to superabrasive particle placement,distances, and sizes, “uniform” refers to dimensions that differ by lessthan about 75 total micrometers.

As used herein, “substantially” when used in reference to a quantity oramount of a material, or a specific characteristic thereof, refers to anamount that is sufficient to provide an effect that the material orcharacteristic was intended to provide. The exact degree of deviationallowable may in some cases depend on the specific context.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be “alittle above” or “a little below” the endpoint.

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. For example, an object that is“substantially” enclosed would mean that the object is either completelyenclosed or nearly completely enclosed. The exact allowable degree ofdeviation from absolute completeness may in some cases depend on thespecific context. However, generally speaking the nearness of completionwill be so as to have the same overall result as if absolute and totalcompletion were obtained.

The use of “substantially” is equally applicable when used in a negativeconnotation to refer to the complete or near complete lack of an action,characteristic, property, state, structure, item, or result. Forexample, a composition that is “substantially free of” particles wouldeither completely lack particles, or so nearly completely lack particlesthat the effect would be the same as if it completely lacked particles.In other words, a composition that is “substantially free of” aningredient or element may still actually contain such item as long asthere is no measurable effect thereof.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also to include allthe individual numerical values or sub-ranges encompassed within thatrange as if each numerical value and sub-range is explicitly recited. Asan illustration, a numerical range of “about 1 to about 5” should beinterpreted to include not only the explicitly recited values of about 1to about 5, but also include individual values and sub-ranges within theindicated range. Thus, included in this numerical range are individualvalues such as 2, 3, and 4 and sub-ranges such as from 1-3, from 2-4,and from 3-5, etc., as well as 1, 2, 3, 4, and 5, individually. Thissame principle applies to ranges reciting only one numerical value as aminimum or a maximum. Furthermore, such an interpretation should applyregardless of the breadth of the range or the characteristics beingdescribed.

The Invention

Vibrating the components involved in a materials removal process canprovide many benefits. Vibrating can provide a re-distribution of forcebetween a tool and a work piece from which material is being removed,thus reducing the directional force of the tool against a work piece. Asa result, addition of a vibrating element to some tools allows the samework to be performed with overall lower force and a lower andredistribution of traditional directional forces. Additionally,vibrations may have a beneficial effect on particle movement. RegardingCMP processing, vibrating various parts of the system in general canoffer various benefits.

For example, one benefit is lower stress polishing, which can greatlyimprove the polishing process particularly with regard to certainpolishing processes. Vibrations introduced between a CMP pad and a wafercan ease the polishing stress at the contact interface and allowpolishing to occur at lower contact pressure, thus reducing thepotential for scratching. Additionally, a lower contact pressuredecreases the shear force and frictional drag that can overheat thecontact interface and damage the wafer or the CMP pad.

Reduced deformation of materials due to reduced contact pressure at theinterface between the CMP pad and the wafer allows polishing operationson softer and more delicate materials that are not typically suited forpolishing by traditional CMP processes. Soft copper circuitry andfragile items that require polishing (i.e. 65 nm or smallerinterconnects) can greatly benefit from vibration being introduced atthe contact interface between the wafer and the CMP pad as the polishingcan be carried out at high speeds with low contact stress to thepolished item, thus efficiently producing an improved polishing.

As another example, vibration can beneficially affect polishing when aslurry is used. Such vibration can cause the slurry to be vigorouslystirred, forcing abrasive particles onto the tips of CMP pad asperities,and thus increasing polishing rate. Furthermore, chemical reactionbetween the slurry and the wafer is accelerated by such vigorousagitation. As one non-limiting example, the oxidation rate of copper canincrease due to such agitation of the slurry due to thorough mixing andthe facilitated movement of ions to and from the copper.

With these principles in mind, the present invention provides methods ofincreasing polishing performance of a CMP process. In one aspect, such amethod can include vibrating a contact interface between a CMP pad and awafer during a CMP process, such that oscillations between the CMP padand the wafer occur in a direction substantially parallel to a workingsurface of the CMP pad.

The present invention also provides methods for improving CMPprocessing. One embodiment includes minimizing drag coefficient onsuperabrasive particles of a CMP pad dresser and associated devices. Theinventors have found that certain vibrations imparted to abrasiveparticles of a CMP dresser during routine conditioning cycles can reducethe drag coefficient imparted on the superabrasive particles which mayresult in many benefits to the CMP pad and dresser itself. For example,a reduced drag coefficient may create CMP pad asperities havingsubstantially uniform heights and CMP pad troughs or grooves havingsubstantially uniform depths. Additionally, the inventors havediscovered that CMP pads possessing such properties can have morepredictable polishing rates and can promote higher quality polishedwafers. Other benefits derived from reduced drag coefficients are CMPpads having an extended service life and reduced wear on thesuperabrasive particles.

Vibrating the CMP apparatus (including any portion of the CMP pad, CMPpad dresser, or wafer), also reduces stick-slip of the materials. Thatis to say that vibrating the pad, dresser, and/or wafer reduces thedirect and potentially harmful contact that they have upon contactingeach other. Often, materials have a tendency to stick on each other (dueto the forces of friction) and then slip. In most applications ofmovement, this effect is not detrimental, damaging or even a hindrance,however, in dealing with materials with such a tight tolerance forthickness and surface variance, these stick-slip effects can be verydamaging. Including a vibrational aspect to CMP allows for moreefficient polishing and dressing. There will be less tearing anddeformation in both processes due to the reduced stick-slip. This isparticularly important to avoid destruction and damage to low Kdielectric and soft copper circuitry. The efficiency of the process isfurther improved by the vibrating in that the consumption of slurry, ifused at all, can be reduced. The vibrating allows for the slurryparticles to be used many more times before it is dislodged, again as aresult of the reduced stick-slip.

As discussed above, CMP pads are typically comprised from a urethanetype material that planarizes wafers by polishing them against arotating CMP pad disc. After several cycles of wafer polishing, a CMPpad dresser must be used to reduce or prevent the working surface of theCMP pad from glazing. Conversely, a CMP pad dresser typically includes ashaft and a rigid and durable substrate having superabrasive particlesattached to an exposed surface of the substrate. There are manydifferent methods for fabricating a CMP pad dresser. Pad dressers may bea slurry-based or a fixed-abrasive type, distinguished by the locationof abrasive particles. In the slurry-based type pads, the particles arein a slurry added to the pad. Alternatively, in fixed-abrasive typepads, the particles are attached to the pad's substrate. Surry isoptional in fixed-abrasive pads. There are various methods for attachingsuperabrasive particles to the working surface of the substrate. Suchmethods and CMP pad devices are described in U.S. Pat. Nos. 6,286,498,6,679,243, and 6,884,155, and U.S. patent application Ser. Nos.10/259,168 and 11/026,544, which are incorporated herein by reference intheir entirety.

All types of pad dressers are considered applicable to the presentinvention. This includes fixed-abrasive and slurry-based pads.Fixed-abrasive pads may include any known in the art, including brazedand electroplated. With fixed-abrasive pads, typically, the substratehas an exposed surface upon which the superabrasive particles are to beaffixed and may be substantially flat or contoured. The substrate isgenerally comprised of a metallic material. The substrate may include avariety of metallic materials. Examples of specific metals includewithout limitation, cobalt, nickel, iron, copper, carbon, and theiralloys or mixtures (e.g. tungsten or its carbide, steel, stainlesssteel, bronze, etc). The superabrasive particles can be brazed orsintered to the exposed surface of the substrate. Alternatively, theparticles can be temporarily attached to the exposed surface prior tobrazing the superabrasive particles thereto. In another embodiment, thesubstrate can be an organic material suitable for having superabrasiveparticles coupled thereto. Such a substrate can include superabrasiveparticles embedded in a resin layer and a metallic layer disposedbetween the particles and the resin layer. This type of configurationmay be desirable in certain working environments where it is highlydesirable or even critical to avoid contaminating a work piece withmetals.

There are various processes that can be used to attach or braze thesuperabrasive particles to the substrate surface. For example, microwavebrazing, vacuum brazing and electroplating. For a brazing process, atemplate having apertures can be placed upon a sheet of brazing alloy.In one aspect of the present invention, the sheet may be a rolled sheetof continuous amorphous brazing alloy. The use of the template allowscontrolled placement of each abrasive particle at a specific location bydesigning the template with apertures in a desired pattern. The desiredpattern can be a grid. A desired uniform pattern such as a grid canallow for proper spacing between each particle. Accordingly, uniformspacing can improve the conditioning performance of the CMP pad dresserby evenly distributing the workload across all of the particles. Afterthe template is placed on the brazing alloy sheet, the apertures can befilled with superabrasive particles. The superabrasive particles canhave a predetermined shape, such as a euhedral, octahedral orcubo-octahedral. Generally, the apertures have a predetermined size, sothat only one abrasive particle will fit in each. Any size of abrasiveparticle or grit is acceptable, however in one aspect of the invention,the particle sizes may be from about 100 to about 350 micrometers indiameter. In another aspect of the invention, the size of the aperturesin the template may be customized in order to obtain a pattern ofabrasive particles having a size within a uniform size range.

A second method for affixing the superabrasive particles to a substratecan be pressing the superabrasive particles into the brazing alloysheet. They may be fixed in the templated position by disposing anadhesive on the surface of the brazing alloy sheet. In this manner, theparticles remain fixed in place when the template is removed and duringheat processing. Attaching the superabrasive particles in this mannerallows for proper depth placement in the substrate such that thesuperabrasive particles extend to a predetermined height above thesubstrate member. In yet another embodiment of the present invention,the template may be laid upon a transfer sheet having a thin adhesivefilm thereon. In this case, the particles become adhered to the transfersheet using the template procedure specified above. The template is thenremoved, and the transfer sheet is laid onto the brazing sheet withabrasive particles facing the sheet. Disposed upon the brazing sheet isthe aforementioned adhesive layer, which is more strongly adhesive thanthe adhesive on the transfer sheet. Therefore, the abrasive particlesare transferred to the sheet of brazing alloy in the pattern dictated bythe template.

Similarly, the transfer sheet may use strategically placed adhesivedroplets instead of a thin adhesive film or layer. This embodiment canreduce the amount of adhesive contaminates that become incorporated inthe brazing process. Additionally, strategically or uniformly placingthe droplets in a predetermined pattern removes the need for using atemplate having apertures as described above. Each adhesive droplet hassufficient strength to adhere a single abrasive particle to each dropletuntil the particles can be transferred to the brazing sheet. A moredetailed description of this process can be found in Applicant'scopending application, Attorney Docket No. 00802-24002, filed on Oct.26, 2006, which is incorporated herein by reference in its entirety.

Finally, the abrasive particles may be coupled to a substrate that ismade of metallic powders. The metallic powders may be selected from anumber of materials known for forming a substrate. Further, the metallicpowder may contain brazing alloys to facilitate the brazing the abrasiveparticles. In a preprocess step, in forming a substrate, the abrasiveparticles are disposed into the metallic powder prior to solidificationor consolidation of the metallic powders. During the brazing or aconsolidation step, the abrasive particles are chemically bonded to thesubstrate, providing a durable CMP pad dresser which may be lessvulnerable to particle chipping and dislodging. Those of ordinary skillin the art will understand a number of variations on the above-recitedgeneral mechanism, and all mechanisms for making CMP pad dressers areconsidered to be within the scope of the present invention.

The superabrasive materials that are suitable for a CMP pad dresser, asdisclosed herein, can be any natural or synthetic diamond, super hardcrystalline, or polycrystalline substance, or mixture of substances andinclude but are not limited to diamond, diamond-like carbon,polycrystalline diamond (PCD), cubic boron nitride (cBN), andpolycrystalline cubic boron nitride (PCBN). As previously noted, thesize of the particles can vary but may be from about 100 to about 350micrometers in diameter.

As mentioned, during a typical CMP pad polishing process a wafer ispressed against a deformable polyurethane CMP pad. As the pad rotates achemical slurry containing micro-sized abrasive grits impregnates intothe grooves and asperities of the CMP pad to aid in the planarization ofthe wafer. Notably, the highest asperities protruding from the CMP padsurface will make the initial contact with the wafer and willcontinually polish the wafer surface throughout the polishing process.During the wafer polishing process, both the wafer and the CMP pad beginto wear. Specifically, the CMP pad asperities that bear the initialcontact of the wafer will begin to wear more rapidly than the otherasperities, thereby creating a CMP pad and polished wafer that varies inthickness and irregularities.

It has now been discovered by the inventors that reducing the dragcoefficients on CMP pad dresser abrasive particles can produce CMP padshaving uniform asperities which promote higher quality polished wafers,longer CMP pad service life, predictable polishing rates and reducedwear on the superabrasive particles of the CMP pad dresser. Therefore,emphasis has been placed on developing methods and devices that canreduce the drag coefficient on the particles such that uniformasperities and uniform grooves in CMP pad working surfaces can becreated.

Traditionally, CMP pad asperities are formed as superabrasive particlescut and plow through the CMP pad while the dresser rotates in a circularmotion and traverses the working surface of the pad, thereby removingdebris from the pad and rejuvenating the asperities of the workingsurface of the pad. Much of the cutting and plowing is accomplished bydragging the particles through the deformable polyurethane material.Such dragging can promote inconsistent, irregular and unpredictablesizes in asperities. Therefore, it can be desirous to reduce thedragging effect such that asperities having uniform heights and depthscan be obtained.

In an embodiment, reducing the effects of drag or drag coefficients onthe superabrasive particles can be accomplished through vibrationsimparted onto the dresser and more specifically onto the superabrasiveparticles of the dresser during the grooming process. The vibrationalmovements of the particles have been found to be effective at improvingthe wear on the particles as well as improving the rejuvenatedproperties of a CMP pad. Functionally, the vibrations can reduce theamount of pad material and frequency that the material comes intocontact with the superabrasive particles. As the superabrasive particlesvibrate at ultrasonic rates and cut into the CMP pad, a consistentportion of material can be displaced on both sides of the superabrasiveparticles thereby creating uniform heights in asperities to promoteuniform polishing of wafers. Additionally, a minimized drag coefficientcan reduce the wear on and extend the service life of the superabrasiveparticles by limiting the amount of contact with the CMP pad materialduring a grooming process.

Accordingly, a method that reduces drag coefficients on CMP padparticles can create CMP pad asperities having substantially uniformheights and troughs having uniform depths. The uniform heights anddepths can be created by the specific vibrations imparted on the dresserparticles. Specifically, the particles can vibrate in either a lateral,circular, elliptical, or any random motion that is substantiallyparallel to the working surface of the CMP pad. In one aspect of thepresent invention, the particles are vibrated laterally, i.e. side toside, such that the dragging is reduced since the amount of padcontacted is reduced. It has also been discovered that the amount ofdrag is significantly reduced when the particles vibrate substantiallyparallel to the working surface of the CMP pad, instead of vibratingperpendicularly or vertically to the working surface of the pad. As aresult, many benefits to the CMP pad and dresser can be obtained, suchas uniform and minimal asperity sizes.

Forming the uniform asperity sizes can be accomplished by using a CMPpad dresser claimed by the present invention as compared to typicalgrooming devices. As the material is constantly displaced by the cuttingand plowing of the CMP pad dresser, the vibrational movements of theparticles minimize the amount of material that is actually dragged byeach superabrasive particle and therefore reduces the overall size ofthe asperities. Alternatively, as mentioned previously, formingasperities having uniform depths can be accomplished by utilizing a CMPpad dresser having superabrasive particles that extend to apredetermined height above the substrate member such that the depth ofthe troughs created correspond to the predetermined height of theparticles. In such embodiments, the total amount of deformable padmaterial that is removed can be maintained at a minimum by way of aconsistent grooming process, as provided. With this in mind, the servicelife of the CMP pad can be extended because the pad itself does not haveto be replaced as often due to the reduced amount of material removedfrom the CMP pad.

Minimal and uniform asperity sizes formed from superabrasive particleshaving a reduced drag coefficient can evenly distribute the workload ofthe CMP pad which, as a result, can also extend the service life of theCMP pad. For example, it has been determined that the workloaddistribution on each asperity determines the polishing rate as well asthe uniformity or planarity of the polished wafer. If the asperityheights become irregular and vary in height, the initial contactasperities will be few. As the polishing process continues, moreasperities will contact the wafer surface, resulting in a decrease incontact pressure and a reduced polishing rate. The contact pressure canactually dictates the polishing rate for each asperity. In other words,wafer contact with few asperities will result in a higher pressure oneach asperity and a higher polishing rate because fewer asperities donot have as much surface area to slow the polishing rate. Further, wafercontact with few asperities can be unstable; the polishing rate willdecrease rapidly as more contacts are being formed. On the other hand,if superabrasive grits can form asperities with more uniform heights,the polishing rate can be more sustainable because more contact pointspromote a more uniformed polishing process resulting in higher qualityfinished wafers. Therefore, the more asperities that come into contactwith the wafer at the commencement of the polishing process, the longerthe polyurethane pad will last.

Vibrators, or a source of vibration, may be located at various locationson the CMP apparatus. The vibrator may be attached to the CMP pad at anylocation that can produce oscillations in a direction substantiallyparallel to the working surface of the CMP pad. Examples includeattachment or coupling to the side or periphery of the CMP pad,attachment to any portion of the underside of the CMP pad (i.e. the padsubstrate that is the opposite side of the working surface, attachmentto the side of the CMP pad, inclusion in any feature attached to the CMPpad (i.e. shafts, backings), etc. Likewise, attachments to the CMP paddresser may be to the side of the substrate, periphery of the workingsurface, on the underside of the dresser, in a shaft or otherencasement, etc. Attachment to the wafer is possible through theinstrument attached to the wafer (such as the retainer ring), or to thewafer directly, via any method known in the art.

In the present invention, the CMP pad dresser or CMP pad can have atleast one vibrator coupled to the dresser at a location that vibratesthe dresser in a direction substantially parallel to a working surfaceof the CMP pad with which the CMP pad dresser is engaged. One vibratorcan be coupled to the CMP pad dresser, although multiple vibrators maybe needed to obtain the proper vibration of the superabrasive particles.With the use of a vibrator, the vibrator can impart vibrations on thesuperabrasive particles of the CMP pad dresser, which in turn can reducethe drag coefficient. The vibrator may be of any type capable ofproducing the herein outlined beneficial vibrations. Anyelectro/mechanical actuation system may be utilized to produce thedesired vibrations. In accordance with one aspect of the presentinvention, the vibrator may be an ultrasonic transducer comprised of apiezoelectric material. Alternatively, the vibrator may be a solenoidwith coils of conducting wire. These embodiments are in no wiselimiting; other vibrator means may be employed. In another embodiment,multiple vibrators such as ultrasonic transducers, solenoids, orcombinations thereof, can be coupled to the dresser at locations thatvibrate the dresser and the particles in a direction that issubstantially parallel to the working surface of the CMP pad. Thevibration may be directionally focused or diffused. Additionally, thevibrations may be amplified by an amplifier or dampened with a dampingplate such as an acrylic board. In some aspects, the vibration may bedirectionally controlled, including back and forth directions, circular,square, figure eight, rectangle, triangle, and other simple or complexdirectional vibration movements and patterns may be used.

More than one vibrator may be used. In one embodiment, the vibrators maybe designed to produce a symmetrical vibration, thus achievingresonance. In another embodiment, the vibrations from multiple sourcescan be asymmetrical, thus causing variation across the pad and/or wafer.This can be favorable in the case where a portion of the pad is leastconsumed, thus the vibrations may be intensified in that area so thatthe pad profile will have the effect of being flat. Such a design canbalance pad usage and is useful to achieve a more uniform thickness orflatter surface of the wafer.

The frequency of the present invention may range from about 1 KHz toabout 1000 KHz. The power range may be from about 1 W to about 1000 W.As previously mentioned, the vibrations imparted on the superabrasiveparticles of the CMP pad dresser originate from a vibrator or avibration means such as piezoelectric transducers. In use, the CMP paddresser or CMP pad can vibrate in either a lateral, circular,elliptical, or random motion substantially parallel to the workingsurface of the CMP pad in addition to the afore mentioned directions.Alternatively, the vibration may be completely in a direction parallelto the working surface of the CMP pad. The piezoelectric transducersshould be suitable to vibrate the particles at ultrasonic frequenciesgreater than 15 kHz. Typically, frequencies higher than those audible tothe human ear, i.e. more than about 15,000 cycles per second, areconsidered ultrasonic. In one embodiment the vibrator can oscillate theparticles at a frequency of about 20 kHz.

In a further embodiment, the ultrasonic vibrations may greatly improvethe process by dispersing slurry particles on the CMP pad. Slurryparticles, either those present as part of a slurry to aid in the CMPprocess, or particles that have been removed from the objects beingpolished, have a tendency to adversely affect the polishing process.These particles may build up on portions of the CMP pad and scratch theobject being polished, e.g. the wafer. Ultrasonic vibrations candisperse the slurry particles and provide a mechanism for more efficientremoval of glazed materials and debris.

In another embodiment of the present invention, the vibrator can beadjusted to control the vibrational movements of the superabrasiveparticles, as well as the drag coefficient of each particle to obtain anoptimal polishing experience. Controlling or adjusting either vibrationfrequency, amplitude or both of the ultrasonic wavelengths can alter thepolishing performance for a given CMP pad dresser. Specifically, higherfrequencies can produce asperities having higher ridges and/or deepertroughs. Alternatively, increasing the amplitude of the ultrasonicvibrations can also affect the asperity sizes, which can produceasperities that allow for more slurry to penetrate in to the pad surfacethereby increasing the overall polishing performance of the system. Inreality, controlling the vibrational frequency and amplitude alters thedrag coefficient on each grooming superabrasive particle which altersthe size of each asperity. Such an embodiment can be conducive forobtaining optimal polishing performance for various applications. Forexample, increasing the frequency and reducing the amplitude may beneeded for optimal polishing of oxide layers on a more brittle wafer. Onthe other hand, reducing the frequency and increasing the amplitude ofthe vibrations can be more effective at polishing metal layers (e.g.copper circuit) on a wafer. Further, controlling the vibrationalproperties may be necessary when other polyurethane-type materials areused form a CMP pad that reacts differently under the pad dressingprocess.

In one embodiment, the vibrating can be continuous or interrupted.Additionally, the vibrating can be performed as part of a plurality ofsteps, or a program wherein different vibrational parameters areselected at specific times during the polishing process. The vibrationalparameters include, without limitation, frequency, amplitude, andsource. In general, large amplitude can cause faster removal but withhigher likelihood of damage, while high frequency at low amplitude canpolish slower but with better finish. Therefore, it logically followsthat a polishing program that starts at a large amplitude and thenchanges to a high frequency low amplitude vibration can be verybeneficial in producing a polished material in faster time, and withbetter finish than polishing with at a single set of vibrationalparameters. The program can change continuously, e.g. changing from alarge amplitude to a slow amplitude over time, or there may be differentand distinct stages, e.g. changing from a large amplitude immediately toa slow amplitude, either with or without a time pause between changing.

By way of another example, with the case of removal of copper, the CMPprocess can be controlled for fast removal initially by high amplitudelow frequency while the copper surface is rough and then it can beramped down to high frequency low amplitude when the end point isapproaching such as when the barrier layer of tantalum nitride isexposed beneath the copper layer. Furthermore, the vibrationalparameters can be modified in accordance to tune to specific conditions,such as addition of slurry, slurry viscosity, new wafer, differentwafer-types, new or different pad conditioners or dressers, and othervariables that reflect changing pad conditions.

In another embodiment, the vibrations may cause the temperature of atleast a portion of the CMP pad to increase by at least about 5° C. Inanother embodiment, the temperature may increase by at least about 20°C.

The following examples present various methods and device and theeffects of reducing the drag coefficient on superabrasive particlesduring a CMP pad conditioning process. Such examples are illustrativeonly, and no limitation on present invention is meant thereby.

EXAMPLES Example 1

An ultrasonic transducer is attached to the side of a typical CMP paddresser. Side meaning on the CMP pad dresser which has an outer wallthat is substantially perpendicular to the working surface of therelated CMP pad. The transducer is attached to this side at a locationthat is not directly in contact with the working surface of the CMP paddresser. When the CMP pad is in use, the CMP dresser can engage the pad,and condition it while vibrating in a direction substantially parallelto the working surface of the CMP pad.

Example 2

An ultrasonic transducer can be attached to the side of a CMP pad. Thelocation and meaning of side is consistent with that of Example 1. Whenthe pad is in use, the CMP dresser can engage the pad and the vibrationscan improve the CMP process.

The above description and examples are intended only to illustratecertain potential embodiments of this invention. It will be readilyunderstood by those skilled in the art that the present invention issusceptible of a broad utility and applications. Many embodiments andadaptations of the present invention other than those herein described,as well as many variations, modifications and equivalent arrangementswill be apparent from or reasonably suggested by the present inventionand the forgoing description thereof without departing from thesubstance or scope of the present invention. Accordingly, while thepresent invention has been described herein in detail in relation to itspreferred embodiment, it is to be understood that this disclosure isonly illustrative and exemplary of the present invention and is mademerely for the purpose of providing a full and enabling disclosure ofthe invention. The foregoing disclosure is not intended to be construedto limit the present invention or otherwise to exclude any such otherembodiment, adaptations, variations, modifications and equivalentarrangements, the present invention being limited only by the claimsappended hereto and the equivalents thereof.

1. A method of increasing polishing performance of a CMP process,comprising: vibrating a contact interface between a CMP pad and a waferduring a CMP process, such that oscillations between the CMP pad and thewafer occur in a direction substantially parallel to a working surfaceof the CMP pad.
 2. The method of claim 1, wherein vibrating the contactinterface includes vibrating the contact interface in a directionsubstantially parallel to the contact interface.
 3. The method of claim1, wherein vibrating the contact interface includes vibrating the CMPpad.
 4. The method of claim 1, wherein vibrating the contact interfaceincludes vibrating the wafer.
 5. The method of claim 1, whereinvibrating the contact interface includes vibrating the CMP pad and thewafer.
 6. The method of claim 1, further comprising decreasing contactpressure at the contact interface as compared to a contact interfacethat is not vibrated to minimize damage to the CMP pad or the wafer. 7.The method of claim 1, wherein vibrations at the contact interfaceinclude a member selected from the group consisting of lateral motions,circular motions, elliptical motions, random motions, and combinationsthereof.
 8. The method of claim 1, further comprising varying vibrationfrequency of the vibrating contact interface.
 9. The method of claim 1,further comprising varying vibration amplitude of the vibrating contactinterface.
 10. The method of claim 1, wherein the contact surface isvibrated at an ultrasonic frequency greater than about 15 kHz.
 11. Themethod of claim 1, wherein the vibrating is continuous vibration. 12.The method of claim 1, wherein the vibrating is intermittent vibration.13. The method of claim 1, wherein the vibrating is two or moresuperimposed vibrations.
 14. A CMP system, comprising: a CMP pad; awafer positioned to contact the CMP pad during a polishing procedure ata contact interface; and a vibration system functionally coupled to atleast one of the CMP pad and the wafer, the vibration system operable tocause vibrations at the contact interface in a direction substantiallyparallel to the contact interface.
 15. The system of claim 14, whereinthe vibration system includes at least one ultrasonic transducer. 16.The system of claim 14, further comprising a CMP pad mounting system forreceiving the CMP pad, wherein the vibration system is coupled to theCMP pad mounting system.
 17. The system of claim 14, further comprisinga wafer mounting system for receiving the wafer, wherein the vibrationsystem is coupled to the wafer mounting system.
 18. A method of CMPprocessing, comprising: bringing into contact a CMP pad and a wafer;moving the CMP pad and the wafer relative to one another to perform aCMP process; and vibrating at least one of the CMP pad and the wafersuch that oscillations between the CMP pad and the wafer occur in adirection substantially parallel to a working surface of the CMP pad.19. The method of claim 18, comprising vibrating the CMP pad.
 20. Themethod of claim 18, comprising vibrating the wafer.